This section provides background information related to the present disclosure which is not necessarily prior art.
Articles of footwear conventionally include an upper and a sole structure. The upper may be formed from any suitable material(s) to comfortably receive, secure, and support a foot on the sole structure. The upper may cooperate with laces, straps, or other fasteners to adjust the fit of the upper around the foot. A bottom portion of the upper, proximate to a bottom surface of the foot, is attached to the sole structure to provide an article of footwear that substantially surrounds a foot during use.
Sole structures generally include a layered arrangement extending between a ground surface and the upper. One layer of the sole structure includes an outsole that provides abrasion-resistance and traction with the ground surface. The outsole may be formed from rubber or other materials that impart durability and wear-resistance, as well as enhance traction with the ground surface. Another layer of the sole structure includes a midsole disposed between the outsole and the upper. The midsole provides cushioning for the foot and is generally at least partially formed from a polymer foam material that compresses resiliently under an applied load to cushion the foot by attenuating ground-reaction forces. Sole structures may also include a comfort-enhancing insole and/or a sockliner located within a void proximate to the bottom portion of the upper that receives a foot during use.
Conventional midsoles typically include a bottom surface disposed on one side that opposes the outsole and a footbed disposed on the opposite side that is contoured to conform to a profile of the bottom surface of the foot. The midsole may be formed from polymer foam materials that are designed with an emphasis on balancing cushioning characteristics relating to softness and responsiveness as the midsole compresses under gradient loads when a downward force is applied thereto, such as during walking or running movements. Midsoles may additionally or alternatively include a fluid-filled bladder that contains a pressurized fluid (e.g., air) that provides cushioning when the fluid-filled bladder compresses under gradient loads.
While a conventional midsole provides adequate cushioning for athletic activities such as running, such midsoles do not provide adaptive or changing support surfaces useful during lateral movements when playing sports such as basketball or tennis. During lateral movements, forces are generally applied to the midsole after the foot has rolled outward toward the lateral side or inward toward the medial side of the midsole. Often the foot is not adequately supported by the midsole by the time the midsole compresses during lateral movements, thereby leaving the foot without a surface on which to bank or push off for optimally performing the lateral movement. While midsoles generally balance responsiveness and support for the foot during typical walking or running movements, creating a midsole that balances responsiveness and support for the foot during lateral movements is difficult to achieve.
Corresponding reference numerals indicate corresponding parts throughout the drawings.